This invention is related to mechanical combination locks. In more specificity, the invention relates to resistant mechanical combination locks and improvements thereto (generally referred to herein as the “locking system”).
In many technical arts, mechanical devices have been superseded by their electronic digital counterparts. The mechanical combination lock (also referred to herein as “combination locks,” “locks,” and “mechanical locks”), however, is time-tested and finds broad use in applications where there may be exposure to moisture or where a backup power supply is not readily available. These applications include, for example, commercial and home safes, vaults, and automated cash machines.
Combination locks, by way of introduction and example, include a plurality (e.g. three or four) wheels, each wheel having a first surface, a second surface, and a peripheral edge. Each wheel's peripheral annular edge has at least one “notch” (also referred to as a “tumbler gate,” “wheel gate,” or “gate”) thereon. The “wheels” are also referred to as “tumbler wheels,” “tumblers,” “tumbler assemblies,” “wheel assemblies,” “tumbler wheel assemblies,” “tumbler rings,” or “gate wheels.” Together wheels are generally jointly referred as the “tumbler stack,” “tumbler pack,” “wheel stack,” or the “wheel pack.” In general, more wheels included in a combination lock make the lock more secure. A “spindle” (also referred to as a “drive shaft”) has a “combination dial” (also referred to as “dial” or “dial plate”) substantially at one end and a “drive cam” (that has at least one “drive cam gate,” “cam gate,” or “gate” on its peripheral annular edge) substantially at the other end. The wheels are positioned around a hub through which the drive shaft is positioned, the wheels being between the combination dial and the drive cam, with the wheel closest to the combination dial being referred to (by convention) as the #1 (or first) wheel, the wheel adjacent the #1 wheel being referred to (by convention) as the #2 (or second) wheel, the wheel adjacent the #2 wheel being referred to (by convention) as the #3 (or third) wheel, and, if present, the wheel adjacent the #3 wheel being referred to (by convention) as the #4 (or fourth) wheel. For purposes of description only, the first surface of each wheel is the surface facing the combination dial and the second surface of each wheel is the surface facing the drive cam. The drive cam has a “drive pin” (an engager such as a raised element, tab, or bump) on it that matches a “wheel fly” (an engager such as a raised element, tab, or bump suitable for interacting with an adjacent drive pin) on the second surface of the #3 wheel (the wheel adjacent to the drive cam, which could also be the #4 wheel if a fourth wheel is present). Each wheel, except the #1 wheel, has a drive pin on its first surface that matches an adjacent wheel fly on the second surface of an adjacent wheel (or the drive cam). The #1 wheel has a wheel fly on its second surface, but does not have a drive pin. When the combination dial is turned (also referred to as “rotated” or “spun”), it rotates the drive shaft and the attached drive cam. When the drive pin on the drive cam interacts with the wheel fly on the adjacent wheel (the #3 wheel in this example), that wheel begins rotating. When the #3 wheel's drive pin interacts with the wheel fly on the adjacent #2 wheel, that wheel begins rotating. When the #2 wheel's drive pin interacts with the wheel fly on the adjacent #1 wheel, that wheel begins rotating. In other words, the sequence repeats so that the adjacent drive pins and wheel flies interact (becoming properly aligned) until all the wheels are rotating together in response to the rotating of the combination dial. This process is called “picking up the wheels” because after several spins, all the drive pins and wheel flies will be matched up and all the wheels will be spinning. When a user stops rotating the dial and turns the dial the other way, the first wheel (the #1 wheel) is left in place. When direction of the rotation changes again, the second wheel (the #2 wheel) is left in place, and so on. When all the wheels have been left in the correct position, the tumbler gates will be aligned and the drive cam gate will be aligned after an additional rotation. Over the wheels rests a bar called the “fence.” The fence stops the lock from being opened by preventing the lever arm nose from engaging the drive cam gate. When the gates in all the wheels are aligned, the fence falls into the slot formed by the aligned gates, allowing the lock to be opened. In other words, the “combination” is reached when the gates in the wheels are aligned.
Combination locks are often described by how many wheels they have. In general, more wheels included in the lock make the lock more secure. In general, for each wheel there is one number in the combination. A combination lock with three wheels, for example, may be referred to as a “three wheel combination lock.” A three wheel combination lock would have three numbers in its combination. Three wheel and four wheel combination locks typically have up to 100 digits on the dial face and thus can provide 106 to 108 permutations for use as a combination.
Persons using combination locks will typically change the combination to a set of numbers known only to them, and in this process can inadvertently fail to set the combination precisely, firmly, and/or correctly, so that the desired combination does not work after the structure to which the lock is attached (e.g. a safe) is closed. Dirt, oils, other residues, or wear on the mechanism can also result in a slipped combination, resulting in what is known in the trade as a “lock out,” where an individual is unable to open his own lock or safe. Restoring access is expensive, disruptive, and requires the services of a professional safe technician (e.g. a locksmith). To avoid this, users are advised to test a new combination several times before closing the lock, but professional safe technicians have found steady work as a result of user haste and slipped or damaged tumblers. Thus there is a need for the ability to more reliably change a combination and yet be able to resist slippage, grit, or residues, and also centrifugal force. A good measure of slip resistance, albeit a destructive test, is a torque test applied to a tumbler wheel assembly. Industry standards perform at up to about 50 or 60 inch-pounds of torque at failure, the point at which the interlock between the gate rings and the combination tumbler ring is lost.
Also of interest in comparing combination locks is an endurance dialing test, where an automated dialer repeatedly rapid dials the combination until it wears out or fails for lack of service. A typical industry benchmark for a high-speed endurance dialing test is about 10,000 complete cycles to failure.
The interlock lever arms or pawls of industry standard combination locks are typically provided with teeth that have not changed much since early patents such as U.S. Pat. No. 901,116 to Murphy (the “Murphy reference”) and U.S. Pat. No. 1,484,692 to Weber (the “Weber reference”). The Murphy reference addresses the issue of the permanence of any adjustment to the combination and proposes a locking dog with inner edge toothed and concaved to conform to the curvature of the outer peripheral edge of the combination tumbler ring it opposes when urged into contact by a rotatable cam. As shown, the locking dog and combination tumbler ring are supplied with sawtooth-shaped teeth. Similarly, the Weber reference discloses a spring-operated lever and tooth surface of a combination wheel, which allows the user having a special change key (cam key) to change the combination when the safe is open. The Weber lever, when the wheel is spun rapidly, may be lifted away from the combination tumbler ring, scrambling the combination set by the user.
U.S. Pat. No. 3,981,167 to Phillips (the “Phillips reference”) again addresses the problem of changing the “combination” for the lock, and provides (see FIGS. 9-10 of the Phillips reference) a locking pawl with pawl teeth. Once the desired orientation between the drive wheel ring and the tumbler ring is accomplished, the pawl is engaged against the drive teeth for holding the two rings together during concurrent rotation. The teeth are generally saw-shaped.
U.S. Pat. No. 3,991,596 to Gartner (the “Gartner reference”) discloses using a locking lever with saw-shaped teeth to secure the tumbler. The art is characterized as follows: “The tumbler wheels 20 generally resemble the changeable tumbler wheels usually employed in combination locks, in that they comprise an inner hub 21 having a serrated outer periphery that is engaged by similar teeth on the jaw formation 22 of a resilient interlocking lever 23 of peripheral or rim portions 24 of the tumbler wheels each having a tumbler gate or peripheral recess 20a therein.”
U.S. Pat. No. 4,312,199 to Uyeda (the “Uyeda '199 reference”) adopts a similar approach, disclosing use of opposing teeth to position a drive member with respect to plastic gate ring (FIGS. 6-8 of the Uyeda '199 reference). The teeth are generally saw-shaped and are not believed to be durable and slip resistant. In U.S. Pat. No. 4,353,231 (the “Uyeda '231 reference”), Uyeda addresses the problem differently, using frictional effects between opposing undulating surfaces to prevent slippage.
U.S. Patent Application Publication No. 2004/0211233 to Jasper (the “Jasper reference”), discloses a key-operated combination change mechanism having four arcuate inner spring arms, each provided with saw-shaped teeth for meshing with teeth on the wheel rings (see paragraph 0062 of the Jasper reference).
Thus it appears that the art as a whole solves the problem of frictional interlocking contact between outer gate rings by interposing teeth having a saw-shaped, serrated, or undulating profile and/or beveled tooth faces. These teeth, by their nature, have surfaces that will tend to ride up on each other when subject to force, are inherently prone to slippage, and, as shown by experience, will generally fail when subjected to 50-60 inch-pounds or less of rotational torque. These tooth designs also are prone to “lock out” when subjected to deposits of grit or other residues that gradually lift the teeth apart.
Finally, it is also known that a combination lock can be defeated by an armed robber using intimidation (duress) to force an individual to dial the combination, or by a very skilled lock manipulator, who senses subtle changes in the smooth operation of the dial to divine all or part of the combination. Many combination locks can be opened by knowing only an approximate combination and by vibrating the dial to drop the fence into the gates.
These problems and other disadvantages of current designs are addressed by the present invention.